Articles made from natural rubber latex generally contain protein, and this may give rise to a variety of undesirable effects in the finished article, including allergic reactions in articles intended for use in contact with human skin, e.g. surgical gloves, medical catheters, household gloves and condoms.
The protein content in rubber latex articles is commonly expressed in two different ways: as total extractable protein (EP) and as protein antigen. The total extractable protein (EP) can be measured, e.g., by the Lowry protein assay. The protein antigen expresses the allergenicity of the protein in the article; it may be measured, e.g., by the ELISA assay method.
A number of methods have been proposed to reduce the protein content or to alleviate the allergic reactions in articles made of natural rubber latex. Thus, Novo Nordisk A/S in Research Disclosure, Mar. 10, 1992, No. 335102 discloses that treatment of latex or latex goods with a protease is effective for changing the proteins to non-antigens and also for reducing the amount total protein in latex goods such as gloves. AU-A-44456/93 (Sumitomo Rubber Ind. & Kao Corp.) discloses a treatment of natural rubber latex with a protease, an anionic surfactant and/or a non-ionic surfactant. AU-A-63069/94 and AU-A-63070/94 (both to Sumitomo Rubber Ind. & Kao Corp.) disclose a treatment of a natural rubber latex with a protease and a surfactant, followed by the addition of, an anionic, amphoteric or non-ionic surfactant, oligomer or polymer, to improve the mechanical stability.